With the mayor battling for a tunnel, the governor pushing for a new viaduct, and Seattle voters wondering if their March 13 vote will even slightly affect the outcome, the future of vehicular transportation along the downtown waterfront remains murky.

Is there a feasible third alternative?

In August, the Washington State Department of Transportation presented to the Seattle City Council with some of the different proposals state engineers had studied on their way to ultimately recommending a six-lane, two-deck tunnel. The bayside wall of the tunnel would double as a long section of a new seawall to be built at the water's edge.

Besides previously considered ideas, state officials also presented two new proposals to the City Council. The could be back for consideration if the advisory election leaves another impass.

"Before issuing the final environmental impact statement, we decided to make sure we were not overlooking anything," said Ron Paananen, project manager for the Washington State Department of Transportation.

State engineers studied nine proposals for replacing the Alaskan Way Viaduct.

Two of the engineering ideas were rejected because they were made of steel.

"We prefer to build concrete bridges wherever we can," Paananen said. It's cheaper to maintain concrete than steel, he said.

Three of the new proposals were variations on a cable-stay bridge. One of the proposals had a single tower while the other two bridges would be designed with two towers. These ideas were deemed too tall and too wide, which increased their visual impact. They also were more costly, Paananen said.

Another idea was to build parallel concrete box girder structures that would stand taller than the existing viaduct. The support columns for the northbound lanes would be set higher than the columns for the southbound lanes. The problem with this idea was it was slightly more expensive and would create a lot of shade on the waterfront, Paananen.

Another rejected, late-breaking idea is called an extrados cable-stayed, concrete, segmental box-girder bridge. It would have seven lanes on a single bridge deck 100 feet off the ground, with towers rising another 50 feet higher.

One disadvantage of that idea is the existing viaduct would have to be torn down before building the bridge, Paananen said. However it also would have encroached on the waterfront and was deemed too expensive.

The final rejected idea, which also had not been previously studied, was a side-by-side bridge. It would look similar to the existing viaduct but with the northbound and southbound lanes on the same level. Stacked above the six lanes would be a pedestrian level with a park or promenade.

The width of the side-by-side proposal would encroach on the waterfront, plus it would shade much of the ground beneath it, Paananen said.

State transportation engineers finally decided a stacked structure similar to the configuration of the existing viaduct would take up the least space, Paananen said.

Advancements in bridge engineering mean a new viaduct could be built with fewer columns, he said. The existing viaduct has a column every 50 feet. A new viaduct could be built with columns needed only every 150 feet.

"We could eliminate two-thirds of the columns," Paananen said.

Regardless of what the state decides to build, hundreds of businesses that rely on the Alaskan Way Viaduct are going to face economic hardship during the years of construction.

Warren Aakervik, owner of Ballard Oil Co., provides fuel to marine industries along the waterfront. At last week's Ballard District Council meeting, he stressed how the coming years of detours and inaccessibility are going to pinch business. Closing the viaduct will cost businesses an estimated $3.4 billion per year, Aakervik said.

"What kind of transportation corridor will we have with no corridor at all?" he asked. "This has major economic implications for the state."

A longtime tunnel opponent, Aakervik's fuel trucks would be prohibited from using a tunnel.

"We have money in hand to build an elevated structure," he said.

Previously the state and city transportation departments recommended building a six-lane, double-decker tunnel. However the Washington Legislature had already appropriated more than $2 billion and legislative leaders made it clear the viaduct project would get no more money.

Mayor Nickels and the Seattle Department of Transportation proposed a smaller, four-lane tunnel. But state officials decided a smaller tunnel would make it difficult for emergency vehicles to get to accident scenes during commuting hours.

Since a four-lane tunnel was determined to be unsafe, combined with the lack of support in the Legislature to spend more money on the project, the governor decided to forge ahead with plans for a new version of the viaduct.

The ballot will ask voters two questions: Do you favor a tunnel, yes or no? Do you favor a new elevated structure, yes or no?

This week, Seattle City Council President Nick Licata will oppose holding the March 13 election, said Newell Aldrich, a legislative assistant to Licata.

"He doesn't see the point of it," Aldrich said.

Tim St. Clair can be contacted at tstclair@robinsonnews.com or 932-0300.